The document discusses landscape graphs and ecological networks. It begins with an overview of the evolution of landscape protection from isolated nature reserves to interconnected ecological networks. It then provides details on constructing landscape graphs by identifying habitat patches and links from landscape maps, including defining minimum patch areas, connectivity thresholds, and cost distances. Metrics for analyzing connectivity are also discussed. The goal is to model ecological networks through landscape graphs to understand habitat connectivity.

1. Xavier Girardet
Laboratoire ThéMA UMR 6049
UBFC / CNRS
Besançon
Modélisation des réseaux
écologiques en écologie
du paysage :
les graphes paysagers
Séminaire Atelier 8 /
ISIG, « Graphes et
réseaux en géographie »

2. De la mise sous cloche.. …aux réseaux écologiques
20001900 2010

3. De la mise sous cloche.. …aux réseaux écologiques
L’émergence d’une discipline
20001900 2010
1970 1980 1990

4. De la mise sous cloche.. …aux réseaux écologiques
L’émergence d’une discipline
Les graphes paysagers
20001900 2010
1970 1980 1990
2001 2006 2008 2012

5. From landscape structures to landscape networks
Artistic movement:
focus on the nature
 Protection of aesthetics landscape
1. De la mise sous cloche.. …aux réseaux écologiques

6. From landscape structures to landscape networks
 Protection of spectacular landscape
1. De la mise sous cloche.. …aux réseaux écologiques

7. From landscape structures to landscape networks
 Protection of flora and fauna
In 1995, Germany had
5,314 nature reserves
1. De la mise sous cloche.. …aux réseaux écologiques

8. From landscape structures to landscape networks
 Protection of flora and fauna
1. De la mise sous cloche.. …aux réseaux écologiques

9. From landscape structures to landscape networks
 Networks of ecosystems
1. De la mise sous cloche.. …aux réseaux écologiques

10. From landscape structures to landscape networks
 Ecological networks
1. De la mise sous cloche.. …aux réseaux écologiques

11. From landscape structures to landscape networks
 Ecological networks
1. De la mise sous cloche.. …aux réseaux écologiques

12. From landscape structures to landscape networks
- Ecological networks
- Landscape connectivity
Structural connectivity Functional connectivity
 Landscape networks
1. De la mise sous cloche.. …aux réseaux écologiques

13. What is landscape ecology ?
Landscape
Ecology
Broad Extents
K. McGarigal
2. L’émergence d’une discipline

14. What is landscape ecology ?
3 fundamental principles
1. The effect of spatial heterogeneity on ecological processes
2. The role of humans
3. A broad spatial scale: the landscape
2. L’émergence d’une discipline

15. The effect of spatial heterogeneity on ecological processes
MacArthur & Wilson (1967): The Theory of Island Biogeography
2. L’émergence d’une discipline

16. The effect of spatial heterogeneity on ecological processes
Forman & Godron (1986) : Landscape mosaic model
2. L’émergence d’une discipline

17. The effect of spatial heterogeneity on ecological processes
Metapopulation models: the first step to landscape connectivity
2. L’émergence d’une discipline

18. The role of humans
Forman (1995): Landscape fragmentation
2. L’émergence d’une discipline

19. A broad spatial scale: the landscape
Delcourt & Delcourt (1988) and Allen & Starr (1988):
The hierarchical theory. Space and time are linked !
2. L’émergence d’une discipline

20. What is a landscape graph ?
Function
Reality
Model
3. Les graphes paysagers

21. 3. Landscape graphs : origins

22. 3. Landscape graphs : the sequel

23. 3. Landscape graphs : the prequel

24. 3. Intégration dans les scenarios de gestion et d’aménagement

25. Construction des graphes paysagers
Construction
des graphes
paysagers

26. Graph construction: identification of habitat patches and links
Landscape map
Suitable elements Barrier elementsOptimal habitat
Friction for species
movements
Minimum patch
area
LANDSCAPE GRAPH
Construction des graphes paysagers

27. Mapping landscape
Input data
Landscape map in raster
format
Categories defined according
to a species/landscape
relation
Usually: cost value (friction)
for each landscape category
Construction des graphes paysagers

28. Defining habitat patches
Patches = graph nodes
o Minimum patch area
o Connexity
o Capacity
Construction des graphes paysagers

29. Defining habitat patches
Patches = graph nodes
o Minimum patch area
o Connexity
4-connexity 8-connexity
Cell adjacent to the orange one
Focal cell
1
3
4-connexity
=> 3 patches
8-connexity
=> 1 patch
2 1
1
1
Construction des graphes paysagers

30. Defining habitat patches
Patches = graph nodes
o Minimum patch area
o Connexity
o Capacity
capacity = intrinsic quality of the patch as
an indicator of its demographic potential
Function of the isotropic
neighbourhood
Area of the habitat patch
Suitable elements Unfavourable elementsHabitat patches
Function of the anisotropic
neighbourhood
Construction des graphes paysagers

31. Defining links
Voronoi
polygon
Construction des graphes paysagers

32. Defining links
Topology
- Complete
- Planar
Direction
Distance
- Euclidean distance
- Least-cost distance
Threshold
Construction des graphes paysagers

33. Defining links
Topology
- Complete
- Planar
Direction
Distance
- Euclidean distance
- Least-cost distance
Threshold
Construction des graphes paysagers

34. Defining links
Topology
- Complete
- Planar
Direction
Distance
- Euclidean distance
- Least-cost distance
Threshold
Construction des graphes paysagers

35. Defining links
Topology
- Complete
- Planar
Direction
Distance
- Euclidean distance
- Least-cost distance
Threshold
Construction des graphes paysagers

36. Defining links
Topology
- Planar
- Complete
Direction
Distance
- Euclidean distance
- Least-cost distance
Threshold
Construction des graphes paysagers

37. Defining links
Topology
- Planar
- Complete
Direction
Distance
- Euclidean distance
- Least-cost distance
Threshold
Construction des graphes paysagers

38. Defining links
Topology
- Planar
- Complete
Direction
Distance
- Euclidean distance
- Least-cost distance
Threshold
Construction des graphes paysagers

39. Defining links
Topology
- Planar
- Complete
Direction
Distance
- Euclidean distance
- Least-cost distance
Threshold
Construction des graphes paysagers

40. Defining links
Land-use categories Function Cost
1 Ponds Habitat 1
2 Water Suitable 10
3 Built-up areas and infrastructures Unfavourable 1000
4 Forests Suitable 10
5 Wetlands Suitable 10
6 Croplands Unfavourable 1000
7 Grasslands Suitable 10
8 TGV line Unfavourable 2000
Construction des graphes paysagers

41. Defining links
Graph threshold
only links shorter than
the threshold distance
are kept.
(maximum dispersal distance
of a given species)
Construction des graphes paysagers

42. Computing connectivity metrics
Several levels:
local
component
global
Many metrics in graph theory…
Rayfield B, Fortin MJ, Fall A, 2011. Connectivity for
conservation: a framework to classify network measures.
Ecology 92: 847-858.
Construction des graphes paysagers

43. Computing connectivity metrics
Sum of capacity of patches
connected to the patch i
i
… weighted according to the
minimum distance to the focal patch
=> indicator of the potential dispersion
from/to the patch i
Similar to the degree index
i i
Construction des graphes paysagers

44. Computing connectivity metrics
Sum of the shortest paths
through the focal patch i.
i
weighted both by the capacity of the two
end patches and by the distance between
them.
=> frequency of use of the patch i
Construction des graphes paysagers